Establecimiento de una conexión TCP

El artículo explica cómo se establece una conexión en TCP, mediante un protocolo en tres fases. Además, indica los bits de la cabecera utilizados, la selección de los números de secuencia iniciales, y los posibles problemas y su solución debidos a la recepción de segmentos de establecimiento de conexión duplicados.Baydal Cardona, ME. (2023). Establecimiento de una conexión TCP. Universitat Politècnica de València. http://hdl.handle.net/10251/19386

El formato de los mensajes DNS

El artículo describe el formato de los mensajes DNS explicando los diferentes campos que lo componen. Además, muestra un par de ejemplos prácticos de uso de las órdenes Linux dig y host que permiten a los usuarios realizar consultas DNS. Así como la interpretación de los resultados obtenidos.Baydal Cardona, ME. (2023). El formato de los mensajes DNS. http://hdl.handle.net/10251/19386

On a course on computer cluster configuration and administration

[EN] Computer clusters are today a cost-effective way of providing either high-performance and/or high-availability. The flexibility of their configuration aims to fit the needs of multiple environments, from small servers to SME and large Internet servers. For these reasons, their usage has expanded not only in academia but also in many companies. However, each environment needs a different ¿cluster flavour¿. High-performance and high-throughput computing are required in universities and research centres while high-performance service and high-availability are usually reserved to use in companies. Despite this fact, most university cluster computing courses continue to cover only high-performance computing, usually ignoring other possibilities. In this paper, a master-level course which attempts to fill this gap is discussed. It explores the different types of cluster computing as well as their functional basis, from a very practical point of view. As part of the teaching methodology, each student builds from scratch a computer cluster based on a virtualization tool. The entire process is designed to be scalable. The goal is to be able to apply it to an actual computer cluster with a larger number of nodes, such as those the students may subsequently encounter in their professional life.This work was supported in part by the Spanish Ministerio de Economia y Competitividad (MINECO) and by FEDER funds under Grant TIN2015-66972-C5-1-R.López Rodríguez, PJ.; Baydal Cardona, ME. (2017). On a course on computer cluster configuration and administration. Journal of Parallel and Distributed Computing. 105:127-137. https://doi.org/10.1016/j.jpdc.2017.01.009S12713710

Teaching high-performance service in a cluster computing course

[EN] Most courses on cluster computing in graduate and postgraduate studies are focused on parallel programming and high-performance/high-throughput computing. This is the typical usage of clusters in academia and research centres. However, nowadays, many companies are providing web, mail and, in general, Internet services using computer clusters. These services require a different ``cluster flavour'': high-performance service and high availability. Despite the fact that computer clusters for each environment demand a different configuration, most university cluster computing courses keep focusing only on high-performance computing, ignoring other possibilities. In this paper, we propose several teaching strategies for a course on cluster computing that could fill this gap. The content developed here would be taught as a part of the course. The subject shows several strategies about how to configure, test and evaluate a high-availability/load-balanced Internet server. A virtualization-based platform is used to build a cluster prototype, using Linux as its operating system. Evaluation of the course shows that students knowledge and skills on the subject are improved at the end of the course. On the other hand, regarding the teaching methodology, the results obtained in the yearly survey of the University confirm student satisfaction.This work was supported in part by the Spanish Ministerio de Economia y Competitividad (MINECO) and by FEDER funds under Grant TIN2015-66972-C5-1-R.López Rodríguez, PJ.; Baydal Cardona, ME. (2018). Teaching high-performance service in a cluster computing course. Journal of Parallel and Distributed Computing. 117:138-147. https://doi.org/10.1016/j.jpdc.2018.02.027S13814711

Progressive congestion management based on packet marking and validation techniques

© 2012 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Congestion management in multistage interconnection networks is a serious problem, which is not solved completely. In order to avoid the degradation of network performance when congestion appears, several congestion management mechanisms have been proposed. Most of these mechanisms are based on explicit congestion notification. For this purpose, switches detect congestion and depending on the applied strategy, packets are marked to warn the source hosts. In response, source hosts apply some corrective actions to adjust their packet injection rate. Although these proposals seem quite effective, they either exhibit some drawbacks or are partial solutions. Some of them introduce some penalties over the flows not responsible for congestion, whereas others can cope only with congestion situations that last for a short time. In this paper, we present an overview of the different strategies to detect and correct congestion in multistage interconnection networks, and propose a new mechanism referred to as Marking and Validation Congestion Management (MVCM), targeted to this kind of lossless networks, and based on a more refined packet marking strategy combined with a fair set of corrective actions, that makes the mechanism able to effectively manage congestion regardless of the congestion degree. Evaluation results show the effectiveness and robustness of the proposed mechanism.This work was supported by the Spanish MEC and MICINN, as well as European Commission FEDER funds, under Grants CSD2006-00046 and TIN2009-14475-C04-01.Ferrer Pérez, JL.; Baydal Cardona, ME.; Robles Martínez, A.; López Rodríguez, PJ.; Duato Marín, JF. (2012). Progressive congestion management based on packet marking and validation techniques. IEEE Transactions on Computers. 61(9):1296-1309. doi:10.1109/TC.2011.146S1296130961

Cálculo de subredes IPv4 del mismo tamaño

Explica con detalle cómo dividir un bloque de direcciones IPv4 en varios bloques más pequeños (subredes) del mismo tamaño y muestra un ejemplo práctico.https://polimedia.upv.es/visor/?id=73f8b330-8ce9-11ec-b9b8-5fa8a1a9fe15Baydal Cardona, ME. (2022). Cálculo de subredes IPv4 del mismo tamaño. http://hdl.handle.net/10251/181494DE

¿Cómo se resuelve un nombre de dominio? Consultas DNS iterativas y recursivas

El video explica cómo se obtiene la dirección IP asociada a un nombre de dominio (resolución de nombre). Para ello diferencia entre la consulta realizada por el cliente inicial (recursiva) y las consultas realizadas entre servidores DNS (iterativas), explicando el proceso de búsqueda entre los propios servidores. También describe cómo puede optimizarse el proceso mediante el uso de cachés.https://media.upv.es/player/?id=47150cf0-79cc-11e6-880c-5f6c827e253cBaydal Cardona, ME. (2018). ¿Cómo se resuelve un nombre de dominio? Consultas DNS iterativas y recursivas. http://hdl.handle.net/10251/100504DE

Fundamentos de transferencia fiable de datos

Introduce los conceptos básicos para conseguir transferencia fiable en una red de computadores, prestando especial énfasis a las estrategias empleadas en los protocolos ARQ (Automatic Repeat Request).https://media.upv.es/player/?id=f5988509-d73f-4e89-a64d-b1814362ecacBaydal Cardona, ME. (2016). Fundamentos de transferencia fiable de datos. http://hdl.handle.net/10251/63583DE

Control de la congestión en TCP: arranque lento y evitación de la congestión

El vídeo explica los dos algoritmos que utiliza el protocolo TCP para evitar la congestión en las redes de computadores. El algoritmo de arranque lento establece como limitar la inyección de paquetes en el caso de ventanas de transmisión pequeñas, mientras el de evitación de la congestión se aplica cuando el tamaño máximo de la ventana de transmisión supera un umbral.https://media.upv.es/player/?id=9ebbefd0-021e-11e6-851a-656f7e06a374Baydal Cardona, ME. (2017). Control de la congestión en TCP: arranque lento y evitación de la congestión. http://hdl.handle.net/10251/81564DE

Direccionamiento IPv4 con y sin clases (CIDR)

El video explica cómo calcular en una dirección IP que bits corresponden al identificador de red y qué parte de la dirección corresponde al identificador de host. Además, permite identificar si una dirección IPv4 es de clase A, B, C o D. Así como justificar porqué se migró al esquema actual de direccionamiento sin clases y la necesidad de las máscaras y los prefijos de red.https://polimedia.upv.es/visor/?id=b33c2640-b737-11eb-8e5b-2f692e8a2388Baydal Cardona, ME. (2023). Direccionamiento IPv4 con y sin clases (CIDR). http://hdl.handle.net/10251/19375